Question

If the atomic mass unit (u) were defined to be one fifth of the mass of $ C-12, $ what would be the atomic weight of Nitrogen in amu?

Answer 1

Hint: We know that the atom is composed of two regions. One region is in the center of the atom containing protons and neutrons are called the nucleus and the other which is the outer region holds electrons in orbit around the nucleus. Protons and neutrons have approximately the same mass as the atomic mass unit (amu).

Complete answer:
Generally, atomic mass is defined as the number of protons or electrons of the atom. Since many elements have isotopes, they use average atomic mass. In the periodic table, the mass of carbon was reported as $ 12.011amu, $ which the average mass of the carbon atom is. The atomic mass on the relative scale is $ C\text{ }\text{ }12 $ and all the masses of the elements are determined relative to $ C\text{ }\text{ }12. $
According to the standard definition According to the standard defined as accurately of the mass of a $ carbon-12 $ atom. Hence, = Average of the proton rest mass and the neutron rest mass. $ \dfrac{1}{12}th $ as accurately of the mass of a carbon-12 atom. Hence, = Average of the proton rest mass and the neutron rest mass.
Using mass spectrometry, the mass of one atom can be measured relative to the mass of another.
We have predefined value of $ C-12=\left[ 1.6\times {{10}^{-34}}gm \right]\times \left[ 12 \right] $
Therefore, $ 1u=1.6\times {{10}^{-34}}=\dfrac{5}{12}u. $
Therefore, here atomic weight of Nitrogen will be $ 14\times \dfrac{5}{12}u=5.83u $

Note:
Remember that the standard unit of the mass of an atom is the atomic mass unit, which is equal to $ \dfrac{1}{12}th $ the mass of an atom $ C\text{ }\text{ }12 $ . The atomic mass unit is also called as Avogram, which is a unit mass and weight equal to one gram divided by Avogadro’s number.